Re: [PATCH] iommu/iova: Sort out rbtree limit_pfn handling

From	Joerg Roedel <joro@8bytes.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] iommu/iova: Sort out rbtree limit_pfn handling
Date	2017-05-17 16:10 +0200
Message-ID	<tI7Oi-43z-13@gated-at.bofh.it> (permalink)
References	<tHIPT-4Yo-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Tue, May 16, 2017 at 12:26:48PM +0100, Robin Murphy wrote:
> When walking the rbtree, the fact that iovad->start_pfn and limit_pfn
> are both inclusive limits creates an ambiguity once limit_pfn reaches
> the bottom of the address space and they overlap. Commit 5016bdb796b3
> ("iommu/iova: Fix underflow bug in __alloc_and_insert_iova_range") fixed
> the worst side-effect of this, that of underflow wraparound leading to
> bogus allocations, but the remaining fallout is that any attempt to
> allocate start_pfn itself erroneously fails.
> 
> The cleanest way to resolve the ambiguity is to simply make limit_pfn an
> exclusive limit when inside the guts of the rbtree. Since we're working
> with PFNs, representing one past the top of the address space is always
> possible without fear of overflow, and elsewhere it just makes life a
> little more straightforward.
> 
> Reported-by: Aaron Sierra <asierra@xes-inc.com>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>

Applied, thanks.

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[PATCH] iommu/iova: Sort out rbtree limit_pfn handling Robin Murphy <robin.murphy@arm.com> - 2017-05-16 13:30 +0200
  Re: [PATCH] iommu/iova: Sort out rbtree limit_pfn handling Aaron Sierra <asierra@xes-inc.com> - 2017-05-16 15:50 +0200
  Re: [PATCH] iommu/iova: Sort out rbtree limit_pfn handling Joerg Roedel <joro@8bytes.org> - 2017-05-17 16:10 +0200

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